About this world
Kepler-399 c is a super-Earth orbiting Kepler-399, a yellow, Sun-like star 2.42 thousand light-years from Earth. It is about 1.4 times the size of Earth. It completes an orbit every 26.7 days at 0.15 AU from its star, closer than Mercury is to the Sun.
Its equilibrium temperature is about 630 K (357 °C): far too hot for liquid water on its surface. By the "cosmic shoreline", it has likely held on to an atmosphere.
It was discovered in 2014 by transit with Kepler. A planet crosses its star and dims it by a tiny, periodic fraction. Kepler-399 has 3 known planets; the others are Kepler-399 b and Kepler-399 d.